The endothelial nitric-oxide synthase-caveolin regulatory cycle.
Nitric oxide production in the vascular endothelium is promoted by diverse agonists that transiently increase intracellular Ca2+ concentration and activate the endothelial nitric-oxide synthase (eNOS), a Ca2+/calmodulin-dependent enzyme. eNOS is acylated by the fatty acids myristate and palmitate and is targeted thereby to plasmalemmal signal-transducing domains termed caveolae. eNOS enzyme activity is markedly attenuated by its interactions with caveolin, the structural scaffolding protein of caveolae. We have discovered that in living cells, the eNOS-caveolin heteromeric complex undergoes cycles of dissociation and re-association modulated by Ca2+-mobilizing agonists. Calcium ionophore A23187 and the muscarinic cholinergic agonist carbachol both promote the dissociation of eNOS from caveolin in cultured cells, associated with translocation of eNOS from caveolae. As [Ca2+]i returns to basal levels, eNOS re-associates with caveolin, and the inhibited enzyme complex is then restored to caveolae, a process accelerated by palmitoylation of the enzyme. These data establish an eNOS-caveolin regulatory cycle, wherein enzyme activation is modulated by reversible protein-protein interactions controlled by Ca2+/calmodulin and by enzyme palmitoylation. Alterations in this cycle are likely to have an important influence on nitric oxide-dependent signaling in the vascular wall.
Feron
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Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Saldana
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Michel
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JB
Michel
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T
D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D051242:Caveolin 1; D022461:Caveolins; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D004789:Enzyme Activation; D008565:Membrane Proteins / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction
D051242:Caveolin 1; D022461:Caveolins; D008565:Membrane Proteins; D011994:Recombinant Proteins; D019001:Nitric Oxide Synthase; D002118:Calcium